Bayer U.S. Pat. Nos. 4,292,233 and 4,417,026 both disclose the combination of a high rubber graft ABS as an impact modifier for PBT.
Societe Chimique des Charbonnages (France) GB 2,171,705 discloses the combination of 3 to 50% PBT with at least one vinyl aromatic monomer and at least one unsaturated nitrile grafted onto a rubber and further blended with a copolymer comprising at least one unsaturated nitrile and at least one vinyl aromatic monomer.
Phillips et al U.S. Pat. No. 2,890,209 describes a family of diepoxides which are useful in maintaining impact performance at high processing temperatures.